<ul class="panel panel-default nav nav-sidebar system">
    <li class="item">
        <a data-toggle="collapse" data-parent="#navbar" 
          href="#collapses">
            系统设置
        </a>
    </li>
    <div class="nav nav-sidebar panel-collapse collapse " id="collapses" >
        <li><a href="#">密码修改</a></li>
        <li><a href="#">二维码绑定</a></li>
        <li><a href="#">帮助</a></li>
    </div>
</ul>